The invention relates to a stent delivery system for use at a bifurcation and, more particularly, a bifurcated stent delivery system having a retractable sheath.
Stents conventionally repair blood vessels that are diseased. Stents are generally hollow and cylindrical in shape and have terminal ends that are generally perpendicular to their longitudinal axes. In use, the conventional stent is positioned at the diseased area of a vessel and, after placement, the stent provides an unobstructed pathway for blood flow.
Repair of vessels that are diseased at a bifurcation is particularly challenging since the stent must overlay the entire diseased area at the bifurcation, yet not itself compromise blood flow. Therefore, the stent must, without compromising blood flow, overlay the entire circumference of the ostium to a diseased portion and extend to a point within and beyond the diseased portion. Where the stent does not overlay the entire circumference of the ostium to the diseased portion, the stent fails to completely repair the bifurcated vessel. Where the stent overlays the entire circumference of the ostium to the diseased portion, yet extends into the junction comprising the bifurcation, the diseased area is repaired, but blood flow may be compromised in other portions of the bifurcation. Unopposed stent elements may promote lumen compromise during neointimalization and healing, producing restenosis and requiring further procedures. Moreover, by extending into the junction comprising the bifurcation, the stent may block access to portions of the bifurcated vessel that require performance of further interventional procedures. Similar problems are encountered when vessels are diseased at their angled origin from the aorta as in the ostium of a right coronary or a vein graft. In this circumstance, a stent overlaying the entire circumference of the ostium extends back into the aorta, creating problems, including those for repeat catheter access to the vessel involved in further interventional procedures.
Conventional stents are designed to repair areas of blood vessels that are removed from bifurcations and, since a conventional stent generally terminates at right angles to its longitudinal axis, the use of conventional stents in the region of a vessel bifurcation may result in blocking blood flow of a side branch or fail to repair the bifurcation to the fullest extent necessary. The conventional stent might be placed so that a portion of the stent extends into the pathway of blood flow to a side branch of the bifurcation or extend so far as to completely cover the path of blood flow in a side branch. The conventional stent might alternatively be placed proximal to, but not entirely overlaying, the circumference of the ostium to the diseased portion. Such a position of the conventional stent results in a bifurcation that is not completely repaired. The only conceivable situation in which the conventional stent, having right-angled terminal ends, could be placed where the entire circumference of the ostium is repaired without compromising blood flow, is where the bifurcation is formed of right angles. In such scenarios, extremely precise positioning of the conventional stent is required. This extremely precise positioning of the conventional stent may result with the right-angled terminal ends of the conventional stent overlaying the entire circumference of the ostium to the diseased portion without extending into a side branch, thereby completely repairing the right-angled bifurcation.
To circumvent or overcome the problems and limitations associated with conventional stents in the context of repairing diseased bifurcated vessels, a stent that consistently overlays the entire circumference of the ostium to a diseased portion, yet does not extend into the junction comprising the bifurcation, may be employed. Such a stent would have the advantage of completely repairing the vessel at the bifurcation without obstructing blood flow in other portions of the bifurcation. In addition, such a stent would allow access to all portions of the bifurcated vessel should further interventional treatment be necessary. In a situation involving disease in the origin of an angulated aorto-ostial vessel, such a stent would have the advantage of completely repairing the vessel origin without protruding into the aorta or complicating repeat access.
In addition to the problems encountered by using the prior art stents to treat bifurcations, the delivery platform for implanting such stents has presented numerous problems. For example, a conventional stent is implanted in the main vessel so that a portion of the stent is across the side branch, so that stenting of the side branch must occur through the main-vessel stent struts. In this method, commonly referred to in the art as the xe2x80x9cmonoclonal antibodyxe2x80x9d approach, the main-vessel stent struts must be spread apart to form an opening to the side branch vessel and then a catheter with a stent is delivered through the opening. The cell to be spread apart must be randomly and blindly selected by recrossing the deployed stent with a wire. The drawback with this approach is there is no way to determine or guarantee that the main-vessel stent struts are properly oriented with respect to the side branch or that the appropriate cell has been selected by the wire for dilatation. The aperture created often does not provide a clear opening and creates a major distortion in the surrounding stent struts. There is no way to tell if the main-vessel stent struts have been properly oriented and spread apart to provide a clear opening for stenting the side branch vessel.
In another prior art method for treating bifurcated vessels, commonly referred to as the xe2x80x9cCulotte technique,xe2x80x9d the side branch vessel is first stented so that the stent protrudes into the main vessel. A dilatation is then performed in the main vessel to open and stretch the stent struts extending across the lumen from the side branch vessel. Thereafter, the main-vessel stent is implanted so that its proximal end overlaps with the side branch vessel. One of the drawbacks of this approach is that the orientation of the stent elements protruding from the side branch vessel into the main vessel is completely random. Furthermore, the deployed stent must be recrossed with a wire blindly and arbitrarily selecting a particular stent cell. When dilating the main vessel stretching the stent struts is therefore random, leaving the possibility of restricted access, incomplete lumen dilatation, and major stent distortion.
In another prior art device and method of implanting stents, a xe2x80x9cTxe2x80x9d stent procedure includes implanting a stent in the side branch ostium of the bifurcation followed by stenting the main vessel across the side branch ostium. In another prior art procedure, known as xe2x80x9ckissingxe2x80x9d stents, a stent is implanted in the main vessel with a side branch stent partially extending into the main vessel creating a double-barreled lumen of the two stents in the main vessel proximal to the bifurcation. Another prior art approach includes a so-called xe2x80x9ctrouser legs and seatxe2x80x9d approach, which includes implanting three stents, one stent in the side branch vessel, a second stent in a distal portion of the main vessel, and a third stent, or a proximal stent, in the main vessel just proximal to the bifurcation.
All of the foregoing stent deployment assemblies suffer from the same problems and limitations. Typically, there are uncovered intimal surface segments on the main vessel and side branch vessels between the stented segments. An uncovered flap or fold in the intima or plaque will invite a xe2x80x9csnowplowxe2x80x9d effect, representing a substantial risk for subacute thrombosis, and the increased risk of the development of restenosis. Further, where portions of the stent are left unopposed within the lumen, the risk for subacute thrombosis or the development of restenosis again is increased. The prior art stents and delivery assemblies for treating bifurcations are difficult to use, making successful placement nearly impossible. Further, even where placement has been successful, the side branch vessel can be xe2x80x9cjailedxe2x80x9d or covered so that there is impaired access to the stented area for subsequent intervention.
Attempts to bring any device, such as a bifurcated stent on a bifurcated balloon assembly, to a bifurcation over two wires are prone to the problem of wire wrapping. This phenomenon involves one wire crossing the other first anteriorly then posteriorly. The resulting wrapping then creates resistance to advancement of the device, thus resulting in failure of deployment. Therefore, when delivering a device ultimately utilizing two wires, it would be desirable to first track the device in over a single wire, thus avoiding wire wrapping. The present invention offers a solution to these problems and others.
As used herein, the terms xe2x80x9cproximal,xe2x80x9d xe2x80x9cproximally,xe2x80x9d and xe2x80x9cproximal directionxe2x80x9d when used with respect to the invention are intended to mean moving away from or out of the patient, and the terms xe2x80x9cdistal,xe2x80x9d xe2x80x9cdistally,xe2x80x9d and xe2x80x9cdistal directionxe2x80x9d when used with respect to the invention are intended to mean moving toward or into the patient. These definitions will apply with reference to apparatus, such as catheters, guide wires, stents, the like. When used with reference to body lumens, such as blood vessels and the like, the terms xe2x80x9cproximal,xe2x80x9d xe2x80x9cproximally,xe2x80x9d and xe2x80x9cproximal directionxe2x80x9d are intended to mean toward the heart; and the terms xe2x80x9cdistal,xe2x80x9d xe2x80x9cdistally,xe2x80x9d and xe2x80x9cdistal directionxe2x80x9d are intended to mean away from the heart, and particularly with respect to a bifurcated blood vessel, are intended to mean in the direction in which the branching occurs.
The invention provides for a bifurcated stent delivery system having a retractable sheath. The system is designed for repairing a main vessel and a side branch vessel forming a bifurcation, without compromising blood flow in other portions of the bifurcation, thereby allowing access to all portions of the bifurcated vessel should further interventional treatment be necessary. The catheter and the retractable sheath are designed to reduce the likelihood of wire wrapping during the stenting procedure.
In one aspect of the invention, there is provided a stent delivery assembly for treating bifurcated vessels including a dual balloon Y-shaped catheter. The catheter includes a first expandable member and a second expandable member. A first guide wire lumen is provided for receiving a first guide wire. The first guide wire lumen extends through at least a portion of the catheter including the first expandable member. A second guide wire lumen is provided for receiving a second guide wire, the second guide wire lumen extends through at least a portion of the catheter including the second expandable member. A tubular member is provided, wherein the first expandable member and the second expandable member are normally biased apart, but are restrained and held together by the tubular member to provide a low profile during delivery of a Y-shaped stent.
In another aspect of the invention, a method is provided of stenting a bifurcated vessel having a bifurcation, a first vessel branch, and a second vessel branch. The method includes the step of providing a dual balloon Y-shaped catheter having a first expandable member and a second expandable member. A Y-shaped stent is mounted on the first and second expandable members. A tubular member is placed about the first and second expandable members such that the first and second expandable members are normally biased apart, but are restrained and held together by the tubular member. The Y-shaped stent is then delivered to a target area. The tubular member is withdrawn proximally until the first expandable member and the second expandable member are released and spring apart. The Y-shaped stent is next implanted by inflating the first and second expandable members. The first and second expandable members are then deflated and the catheter is withdrawn.
In yet another aspect of the invention, a method is provided of stenting a bifurcated vessel having a bifurcation, a first vessel branch, and a second vessel branch. The method includes the step of providing a dual balloon Y-shaped catheter including a first expandable member and a second expandable member. A first guide wire lumen is provided for receiving a first guide wire. The first guide wire lumen extends through at least a portion of the catheter including the first expandable member. A second guide wire lumen is provided for receiving a second guide wire. The second guide wire lumen extends through at least a portion of the catheter including the second expandable member. A Y-shaped stent is mounted on the first and second expandable members. A tubular member is placed about the first and second expandable members such that the first and second expandable members are normally biased apart, but are restrained and held together by the tubular member. A second guide wire is positioned distally of the bifurcation in the first vessel branch. The second guide wire is then backloaded into the second guide wire lumen. Next, the catheter and tubular member are advanced over the second guide wire so that the catheter is advanced distally of the bifurcation in the first vessel branch. Alternatively, the catheter can be advanced proximally of the bifurcation in the first vessel branch. The tubular member is withdrawn proximally until the first expandable member and the second expandable member are released and spring apart. Next, the catheter is withdrawn proximally to a position proximal of the bifurcation. A first guide wire is provided and advanced out of the first guide wire lumen and into the second vessel branch distally of the bifurcation. The catheter is advanced distally over the first and second guide wires until the Y-shaped stent is positioned at the bifurcation. The Y-shaped stent is then implanted by inflating the first and second expandable members. The first and second expandable members are deflated and the catheter and guide wires are withdrawn.
Other features and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention.